阅读说明：本技术 一种无污染的钢铁气体发黑工艺 (Pollution-free steel gas blackening process ) 是由 徐德照 于 2019-11-18 设计创作，主要内容包括：本发明公开一种无污染的钢铁气体发黑工艺,包括如下步骤：零件清理；零件装炉,同时往炉内装入催化剂；抽真空排出炉内空气；充入氮基保护性气氛,加热到500～600℃,转入脉冲抽排气,加热时间为60～120min；降温到氧化处理温度400～500℃,将炉内的氮基保护性气氛转换为氧化性气氛,保温持续时间为30～300min；抽去氧化性气氛,充入氮气,降温到200～480℃；零件出炉并浸油；零件冷却后出油。与普通碱性发黑相比,本发明可以使零件耐腐蚀性能提高50％～200％。本发明工艺过程加入的原料为氮气、氨气和氧气,最终排放的气体为氮气、氧气和少量氢气,这是一个无污染工艺。(The invention discloses a pollution-free steel gas blackening process, which comprises the following steps: cleaning parts; loading the parts into a furnace, and simultaneously loading a catalyst into the furnace; vacuumizing to discharge the air in the furnace; filling nitrogen-based protective atmosphere, heating to 500-600 ℃, and then performing pulse exhaust for 60-120 min; cooling to the oxidation treatment temperature of 400-500 ℃, converting the nitrogen-based protective atmosphere in the furnace into an oxidizing atmosphere, and keeping the temperature for 30-300 min; pumping out oxidizing atmosphere, filling nitrogen, and cooling to 200-480 ℃; discharging the parts out of the furnace and soaking the parts in oil; and (6) discharging oil after the part is cooled. Compared with the common alkaline blackening, the invention can improve the corrosion resistance of the parts by 50-200%. The raw materials added in the process of the invention are nitrogen, ammonia and oxygen, and the finally discharged gas is nitrogen, oxygen and a small amount of hydrogen, which is a pollution-free process.)

1. A pollution-free steel gas blackening process is characterized by comprising the following steps:

s01, cleaning parts;

s02, charging the parts into a furnace, and simultaneously charging a catalyst into the furnace;

s03, vacuumizing to discharge air in the furnace;

s04, filling nitrogen-based protective atmosphere, heating to 500-600 ℃, and transferring to pulse exhaust for 60-120 min;

s05, cooling to the oxidation treatment temperature of 400-500 ℃, converting the nitrogen-based protective atmosphere in the furnace into an oxidizing atmosphere, and keeping the temperature for 30-300 min;

s06, exhausting oxidizing atmosphere, filling nitrogen, and cooling to 200-480 ℃;

s07, discharging the parts out of the furnace and immersing the parts in oil;

and S08, cooling the parts and discharging oil.

2. The non-polluting steel gas blackening process of claim 1 wherein in step S01, the machined part is wiped with a clean dry cloth to remove surface oil stains.

3. The non-polluting steel gas blackening process of claim 1, wherein the rusted and cast part surface is shot-blasted in step S01.

4. The non-polluting steel gas blackening process according to claim 1, wherein in step S02 the catalyst is solid crystalline ammonium chloride.

5. A non-polluting steel gas blackening process according to claim 4, wherein the amount of added crystalline ammonium chloride is: effective volume of furnace (m)³)×(12～30g)/m³。

6. The non-polluting steel gas blackening process according to claim 1, wherein the catalyst is gaseous catalyst ammonia in step S02.

7. The non-polluting steel gas blackening process according to claim 6, wherein the nitrogen based protective atmosphere is nitrogen or a mixed gas of nitrogen and ammonia in step S04.

8. The non-polluting steel and iron gas blackening process according to claim 7, wherein the amount of ammonia gas as the gaseous catalyst added in step S02 and nitrogen gas as the gaseous catalyst added in step S04 is 1: 1.

9. the non-polluting steel gas blackening process of claim 1 wherein in step S05 the oxidizing atmosphere has the composition: 80-95% of nitrogen and 5-20% of oxygen.

Technical Field

The invention relates to a steel surface protection technology, in particular to a pollution-free steel gas blackening process.

Background

The alkaline solution blackening technology is used for blackening (essentially in an oxidation process) the surface of steel, is a common process method for protecting the surface of steel and reducing oxidation and rusting at present, and is simple in process and easy to obtain a uniform black or blue-black surface. The method is the cheapest and most practical method in all steel surface protection treatments, so the method is widely applied to various industries such as machinery, electrical appliances and the like.

The heating blackening technology for the alkaline solution is obtained by boiling a high-concentration solution consisting of sodium hydroxide, sodium nitrite and water at the temperature of about 150 ℃ for 10-100 min.

The general process flow for alkaline blackening is as follows: alkali solution rust removal → cold and hot water exchange cleaning → acid solution oil removal → cold and hot water exchange cleaning → alkaline oxidation solution blackening treatment → cold and hot water soap and water exchange cleaning → drying → hot immersion oil.

The existing alkaline solution blackening technology has the following problems:

(1) pollution problem

A. The derusting and deoiling in the process can cause a large amount of chemical solution to be discarded, the direct discharge can cause pollution, and the cost is higher if the solution needs to be treated;

B. the alkaline blackening liquid generally needs to be replaced or replaced in a large proportion after being used for several months, and a large amount of high-concentration chemical waste liquid generated in the process is difficult to treat;

(2) the working environment is severe, and the working conditions are deteriorated by high-temperature steam and the completely exposed working environment;

(3) high-concentration high-temperature alkali liquor is easy to cause personal injury.

Recent developments in alkaline blackening processes:

(1) the blackening process at normal temperature is a new process developed in recent years, aims to improve the working conditions, uses a high-concentration alkaline solution as a raw material, and is not accepted by the market at present because the blackening process is extremely unstable.

(2) The method is characterized in that the part is directly put into a blackening solution to finish blackening by utilizing the tempering waste heat of the medium-temperature tempering part, and the solution used by the method is a neutral solution, but the method has great application limitation and can only be applied to a continuous furnace for medium-temperature tempering.

In addition to the above-described alkaline solution blackening technique, there is also a QPQ technique. The technology is to add surface oxidation on the surface of a hardened layer obtained by nitrocarburizing, and the purpose of increasing the oxidation is to improve the corrosion resistance and color uniformity of the surface. This is a technique for hardening the surface as a main purpose.

QPQ is classified into two types of salt bath and gas:

1. salt bath QPQ:

(1) it adopts nitrocarburizing salt and oxide salt in a high-temperature melting state to respectively realize nitrocarburizing and oxidation;

(2) the service temperature of the nitrocarburizing salt bath is 560 ℃, the treatment time is different according to the thickness of the nitriding layer required by the product, and is generally not less than 2 hours; the use temperature of the oxidation salt tank is 390 ℃, and the treatment time is generally 30-40 min;

(3) the process comprises the following steps: cleaning parts, generally adopting a volatile solvent → preheating, wherein the temperature is 380 ℃ → salt bath nitrocarburizing → transferring to an oxidation tank for oxidation → hot water repeated soaking and cleaning → drying and oil soaking → checking and packaging;

(4) advantages of salt bath QPQ: the technology can enable the surface of the part to obtain a bearing layer and a high wear-resistant layer with certain thickness at lower temperature, and is widely applied to various light-load precision parts due to low treatment temperature and small deformation (namely, the minimum deformation in various heat treatment hardening processes);

(5) disadvantages of salt bath QPQ: a. the cost is high, as the salt bath raw materials are too specialized, specialized commercial salt or imported salt is generally adopted, and meanwhile, in the treatment process, as the temperature of the salt bath is low, a large amount of molten salt is brought out along with parts, so that the cost is increased, and the treatment price of the salt bath QPQ in the current market is generally 15-30 yuan/kg, which is higher than most of heat treatment process types; b. the treatment process is toxic, and although professional commercial salt can be nontoxic and pollution-free, a large amount of ammonia gas can be generated in the treatment process, and cyanate radicals can be generated in the molten salt bath, so that the material is a substance with high toxicity; c. waste salt and waste liquid for cleaning parts need environmental protection treatment;

2. gas oxynitridation (also called gas QPQ)

(1) After a bearing layer and a wear-resistant layer with certain thickness are obtained on the surface in gas nitriding, a surface oxidation procedure is added to finally obtain a blue-black oxidized surface, so that the corrosion resistance of the surface can be further improved;

(2) the treatment temperature is 560 ℃;

(3) the process comprises the following steps: cleaning parts, generally adopting a volatile solvent → charging (gas nitriding furnace) → vacuumizing → filling nitrogen for protection and heating → converting into nitriding atmosphere → nitriding → converting into oxidizing atmosphere → oxidizing → reducing the temperature to a certain temperature → discharging and oil immersion → checking and packaging;

(4) the process time is as follows: the nitriding process is similar to common gas nitriding, and needs longer process time, and the process time is usually 6-20 hours according to different hardened layer requirements;

(5) advantages of gas oxynitridation: a. the bearing layer and the high wear-resistant layer with certain thickness can be obtained on the surface of the part at a lower temperature, and the deformation is small; b. the main process can be completed in the same furnace body, and the operation is simple and convenient;

(6) the disadvantages of gas oxynitridation: a. the cost is high because the process time is long and the cost is high, and the price of the current market is generally 12-20 yuan/kg, which is higher than most heat treatment process types; b. the nitriding process has a certain amount of residual ammonia gas discharged, and proper treatment is necessary, otherwise, the environment is influenced.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provide a pollution-free steel gas blackening process.

The purpose of the invention is realized by the following technical scheme:

a pollution-free steel gas blackening process comprises the following steps:

s01, cleaning parts;

s02, charging the parts into a furnace, and simultaneously charging a catalyst into the furnace;

s03, vacuumizing to discharge air in the furnace;

s04, filling nitrogen-based protective atmosphere, heating to 500-600 ℃, and transferring to pulse exhaust for 60-120 min;

s05, cooling to the oxidation treatment temperature of 400-500 ℃, converting the nitrogen-based protective atmosphere in the furnace into an oxidizing atmosphere, and keeping the temperature for 30-300 min;

s06, exhausting oxidizing atmosphere, filling nitrogen, and cooling to 200-480 ℃;

s07, discharging the parts out of the furnace and immersing the parts in oil;

and S08, cooling the parts and discharging oil.

In one embodiment, in step S01, the machined part is wiped with a clean dry cloth to remove surface oil stains.

In one embodiment, in step S01, the rusted and cast part surface is shot peened.

In one embodiment, in step S02, the catalyst is solid crystalline ammonium chloride.

In one embodiment, the amount of crystalline ammonium chloride added is: effective volume of furnace (m)³)×(12～30g)/m³。

In one embodiment, in step S02, the catalyst is gaseous catalyst ammonia.

In one embodiment, in step S04, the nitrogen-based protective atmosphere is nitrogen or a mixed gas of nitrogen and ammonia.

In one embodiment, the amounts of ammonia gas as the gaseous catalyst added in step S02 and nitrogen gas added in step S04 are 1: 1.

in one embodiment, in step S05, the oxidizing atmosphere has a composition of: 80-95% of nitrogen and 5-20% of oxygen.

When only a solid catalyst ammonium chloride is used, carrying out a salt spray test on the parts to rust for 24-48 h; when a solid catalyst ammonium chloride and a gas catalyst ammonia gas are used at the same time, the rusting time in a salt spray test is 72-100 h; the rusting time of the existing common alkaline blackening part in the salt spray test is only 6-15 h; compared with the common alkaline blackening, the invention can improve the corrosion resistance of the parts by 50-200%.

The raw materials added in the process of the invention are nitrogen, ammonia and oxygen, and the finally discharged gas is nitrogen, oxygen and a small amount of hydrogen, so the process is a pollution-free process. The catalyst added in the process is small in amount, most of the catalyst is decomposed in the process, and even if part of undecomposed (mainly ammonia gas) is discharged out of the furnace body, the part of undecomposed (mainly ammonia gas) is filtered by a sealed water tank or passes through a cracking device, and only nitrogen, oxygen and hydrogen are discharged finally.

According to the invention, the program control equipment with higher automation degree is adopted, so that the whole process can be automatically completed by only pressing one button when a worker operates, 2-4 equipment can be managed by one worker, and the production cost is reduced due to less labor, cleanness and no pollution; the technological process is carried out in a vacuum sealed furnace body except charging and discharging, and the whole working environment is good.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.

FIG. 1 is a flow chart of the steps of a non-polluting steel gas blackening process according to an embodiment of the present invention.

Detailed Description

To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

It will be understood that when an element is referred to as being "secured to" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "left," "right," and the like as used herein are for illustrative purposes only and do not represent the only embodiments.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

The invention discloses a pollution-free steel gas blackening process, which comprises the following steps:

s01, cleaning parts;

the surface oil stain of the parts machined by the common machine is wiped by clean dry cloth, and the surface of the rusted and cast parts is treated by shot blasting; in the invention, the treated part is steel, has blue-black color, and has similar color with the part treated by common alkaline blackening.

S02, charging the parts into a furnace, and simultaneously charging a catalyst into the furnace;

in this process, the catalyst is preferably solid crystalline ammonium chloride, which is added in the following amounts: effective volume of furnace (m)³)×(12～30g)/m³In this embodiment, the effective volume of the furnace chamber is calculated in cubic meters. The addition of the crystallized ammonium chloride utilizes the decomposition of the ammonium chloride at high temperature to generate chloride ions which can further clean the surface of the part, thereby obtaining more uniform blue-black surface color.

In addition, the gaseous catalyst ammonia can be selected, the ammonia is added to activate the surface of the part, and the activation process is as follows: the ammonia gas can be decomposed into H at high temperature₂And active nitrogen ions which form iron nitrogen compounds with iron atoms, i.e., an initial nitrided layer, which cannot form an effective white layer due to a short action time and replace nitrogen atoms with oxygen atoms in a subsequent oxidation process, thereby obtaining dense Fe₃O₄And the protective layer can further improve the corrosion resistance of the treated part.

Further, the solid catalyst, crystalline ammonium chloride and the gaseous catalyst, ammonia gas, can also be simultaneously added into the furnace.

S03, vacuumizing to discharge air in the furnace;

s04, filling nitrogen-based protective atmosphere, heating to 500-600 ℃, and transferring to pulse exhaust for 60-120 min;

this step, the main purpose of which is to evacuate the oil vapours volatilized from the parts; the catalyst added in step S02 is mainly used in this vacuum heating degreasing phase, in order to clean and activate the part surface;

it should be noted that, in this process, the pulse exhaust gas is to continuously pump the nitrogen-based protective atmosphere into the furnace and continuously pump the nitrogen-based protective atmosphere out of the furnace, and the vacuum pulse technique is used to keep the nitrogen-based protective atmosphere in contact with the surface of the part in a certain freshness, which is important for obtaining uniform color on the surface of the part.

In this embodiment, the nitrogen-based protective atmosphere is nitrogen or a mixed gas of nitrogen and ammonia, and the amount of the gaseous catalyst ammonia added in step S02 and the nitrogen added in step S04 is 1: 1.

s05, cooling to the oxidation treatment temperature of 400-500 ℃, converting the nitrogen-based protective atmosphere in the furnace into an oxidizing atmosphere, and keeping the temperature for 30-300 min;

in the process, the rapid replacement of furnace gas is realized by utilizing a vacuum technology, and particularly, the nitrogen-based protective atmosphere is rapidly converted into an oxidizing atmosphere.

In this example, the composition of the oxidizing atmosphere is: 80-95% of nitrogen and 5-20% of oxygen.

S06, exhausting oxidizing atmosphere, filling nitrogen, and cooling to 200-480 ℃;

s07, discharging the parts out of the furnace and immersing the parts in oil;

and S08, cooling the parts and discharging oil.

The method is characterized in that when only a solid catalyst ammonium chloride is used, the rusting time of the part is 24-48 h in a salt spray test; when a solid catalyst ammonium chloride and a gas catalyst ammonia gas are used at the same time, the rusting time in a salt spray test is 72-100 h; the rusting time of the existing common alkaline blackening part in the salt spray test is only 6-15 h; compared with the common alkaline blackening, the invention can improve the corrosion resistance of the parts by 50-200%.

The raw materials added in the process of the invention are nitrogen, ammonia and oxygen, and the finally discharged gas is nitrogen, oxygen and a small amount of hydrogen, so the process is a pollution-free process. The catalyst added in the process is small in amount, most of the catalyst is decomposed in the process, and even if part of undecomposed (mainly ammonia gas) is discharged out of the furnace body, the part of undecomposed (mainly ammonia gas) is filtered by a sealed water tank or passes through a cracking device, and only nitrogen and oxygen are discharged finally.

According to the invention, the program control equipment with higher automation degree is adopted, so that the whole process can be automatically completed by only pressing one button when a worker operates, 2-4 equipment can be managed by one worker, and the production cost is reduced due to less labor, cleanness and no pollution; the technological process is carried out in a vacuum sealed furnace body except charging and discharging, and the whole working environment is good.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.